2021 Belgrade Challenger – Men's singles

This was the first of the three tournaments held in Belgrade for the 2021 tennis season. Belgrade also hosted a joint ATP/WTA tournament.

Roberto Carballés Baena won the title after defeating Damir Džumhur 6–4, 7–5 in the final.

Seeds
• # 🇪🇸 Roberto Carballés Baena (champion)

• # 🇦🇷 Facundo Bagnis (quarterfinals)

• # 🇨🇴 Daniel Elahi Galán (first round)

• # 🇩🇪 Philipp Kohlschreiber (second round)

• # 🇦🇷 Francisco Cerúndolo (first round)

• # 🇯🇵 Taro Daniel (quarterfinals)

• # 🇧🇴 Hugo Dellien (second round)

• # 🇫🇷 Benjamin Bonzi (second round)